Nearly 5.8 million Americans have heart failure. As doctors explain it, excess fluid can accumulate in the body when the heart isn't working properly, as happens in people with heart failure.

Drugs called loop diuretics -- also called "water pills" -- help remove excess fluid, but also flush potassium, a mineral, out of the body.

"For the heart failure population, diuretics are a common and necessary part of a patient's daily regimen," said Dr. Tara Narula, associate director of the Cardiac Care Unit at Lenox Hill Hospital in New York City. "Unfortunately they come with the common side effect of potassium depletion, which can lead to dangerous heart rhythm disturbances."

Because of that, many doctors prescribe potassium supplements to heart failure patients taking diuretics. According to the authors of the new study, theirs is the first to examine the survival benefits of potassium supplements in this group of patients.

Researchers led by Charles Leonard, a senior research investigator in the University of Pennsylvania's Center for Clinical Epidemiology and Biostatistics (CCEB), analyzed data from about 360,000 Medicaid patients with heart failure who began taking diuretics between 1999 and 2007. Half of them also took potassium supplements.

The overall death risk among all patients in the study was 9 percent per year, the researchers said.

However, among patients who took at least 40 milligrams (mg)/day of a diuretic called furosemide, those who also took a potassium supplement had a 16 percent lower risk of death, according to the findings published online July 16 in the journal PLoS One.

Among patients who took less than 40 mg/day of furosemide, those who took a potassium supplement still had a 7 percent lower risk of death.

"Because this is the first such study of this question, we hope that others confirm these results in independent studies," Leonard said in a university press release.

"Using potassium supplementation for patients receiving loop diuretic therapy may be a relatively inexpensive way to save lives," senior author Sean Hennessy, associate professor of epidemiology in the CCEB, said in the news release. "In today's climate of seeking cost-effective measures to keep patients healthy, this is a therapy that certainly merits additional consideration."

For her part, Narula said the study is valuable and unique because, "the potassium use was for prevention, as opposed to only in patients with documented low potassium."

She believes that "further studies are warranted but this may signal a need to change practice and begin routinely prescribing potassium to heart failure patients on diuretics."

Dr. Ajith Nair works in the Advanced Heart Failure and Transplantation Program at The Mount Sinai Hospital in New York City. He agreed with Narula, saying that "this study emphasizes the need for potassium supplementation with use of higher-dose loop diuretics."